The present invention relates to a low-loss slidable connection of an antenna and more particularly to a low-loss slidable connection of a satellite antenna to a satellite mobile radio. Even more particularly, the invention relates to a low-loss slidable connection for a satellite antenna wherein a satellite telephone maintains communication as the satellite antenna slides through a continuum of positions.
The ability to maintain low-loss communication at all times while a satellite antenna is moved throughout a continuum of positions is important to quick and efficient use of a satellite mobile radio (or satellite telephone), or other mobile radio. If communication is degraded heavily during repositioning of the satellite antenna, communication between the satellite telephone and a satellite station or base station may be lost completely requiring a caller to reinitiate a telephone call. Such degraded performance or a design causing disconnection of the satellite antenna during repositioning is clearly problematic and inefficient.
There is a current need in the industry of antenna design for an improved design for a continuously low-loss connection with a satellite antenna. Solutions developed for connecting cellular antennas cannot be used as they are far too lossy for satellite applications.
Non-satellite antennas, such as conventional cellular antennas generally have a simpler structure than do conventional satellite antennas. A typical cellular antenna consists of a linear conductive member. Thus, connecting a simple antenna such as a cellular antenna through a slidable connection does not present as many challenges as does connecting a satellite antenna thereto. The reason for this is the complexity of the satellite antenna.
A conventional satellite antenna consists of more than just one wire. For example, a quadrafiler helix (QFH) satellite antenna consists of pairs of conductive windings around a cylindrical shell in a helix geometry. Because the satellite antenna is a bundle of wires wound in a helix (with each wire or group of wires requiring a separate connection) rather than a single conductive member, a single sliding connection cannot be effected as in a cellular environment.
For example, in the case of four (4) pairs of wires wound into a helix spiraling around the cylindrical shell of the antenna, a connection must be made to all of four (4) pairs of helix-wound wires. So, as the satellite antenna slides the connection must be made with specific varying points on the Quadrafiler Helix (QFH) satellite antenna. That is, four (4) such pairs of helix-wound wires create eight (8) windings all at different locations of the cylindrical shell at any given length of the satellite antenna.
Therefore, the satellite antenna cannot connect slidably in the satellite telephone as does a cellular antenna in a cellular telephone, and a different solution must be achieved. The problem is thus to make an low-loss electrical connection to a static mobile radio with a sliding antenna, whether the sliding antenna be a cellular antenna, a satellite antenna, or some combination of both.
This problem is also especially peculiar to satellite antennas because a satellite communication system can tolerate a lesser amount of signal losses than a cellular communication system can tolerate. A high-loss system is particularly problematic in satellite telephones because of a limited loss budget. In order to make up this loss on the satellite side, e.g., by building a more sophisticated satellite, extremely high costs would be involved.
The applicants are currently unaware of any prior art to the slidable connection taught herein by the Applicants. The applicants are also unaware of any publically available designs or mobile radio products achieving a near loss-less slidable connection to a satellite antenna.
However, an alternate, less effective, method of achieving the near loss-less slidable connection by a mobile radio to the satellite antenna is currently under development by the Applicants using cables attached to a single basal connection point on the satellite antenna for the pairs of helix-wound wires. A cable is connected at one end to each of the basal connection points and at another end to a printed circuit board of the satellite telephone. Such a prototype handset, under development by Hughes Network Systems (HNS) is called "Thuraya" and has not yet been publically exploited.
Though the use of cables in a slidable connection for the satellite antenna is mechanically reliable, it is inherently clumsy, difficult and expensive to manufacture or repair because of costs and time involved with manual assembly. There are many costs involved with manually assembling the cables into the satellite telephone. Additionally, a cabled connection is not easily disconnected to enable re-connection of the satellite telephone to another antenna system.
More losses are also inherent in the use of the cable as compared to the instant invention, and increase with the length of the cable. In general, an embodiment of the instant invention would likely achieve a 0.2 dB to 0.3 dB increase in performance over the use of cables for the slidable connection.
Another way to achieve more than one position in connecting the satellite antenna to the transceiver is to set two satellite antenna positions via a swivel antenna using a shoulder joint. Unfortunately, this does not solve the problem of maintaining a continuous connection while sliding the satellite antenna from a retracted to an extended position.
The present invention advantageously addresses the above and other needs.